Frequency to Digital Converter based on Rational Approximation Technique for FMCW LiDAR Receiver

This work presents the design and implementation of the Frequency to Digital Converter (FDC) architecture suit-able for Frequency-Modulated Continuous Wave (FMCW) Light Detection and Ranging (LiDAR) application. The implemented FDC can be used at the back-end of the FMCW LiDAR for the conversion of beat frequency (i.e., the instantaneous frequency difference between transmitted and received signal) into digital bits, which can be used to estimate the distance between the LiDAR system and the target object. The FDC specifications are based on LiDAR system parameters. The rational approximation-based method is used to convert the frequency into digital bits; this architecture is suitable for large frequency range measurements. This paper presents frequency measurements from 2 MHz to over 50 MHz with a resolution of less than 10 kHz, which was implemented and tested on hardware using the SoC FPGA.